ERBB2 and breast cancer: Moreover, in the ATEMPT trial, which randomized patients with stage I HER2 + BC to receive adjuvant T-DM1 or the APT regimen, among 114 patients treated with the APT regimen, 9 experienced iDFS events consistent with a 5-year iDFS of 91.1% (95% CI, 85.7–96.8), and 5-year RFI of 93.2% (95% CI, 88.5–98.2)13.